cas 583-78-8, 2,5-Dichlorophenol | Articles data

Articles about 583-78-8Total 49 be found

Article title
Article abstract
Author
Journal number and time
Download

New metabolites in the degradation of α- and γ- hexachlorocyclohexane (HCH): Pentachlorocyclohexenes are hydroxylated to cyclohexenols and cyclohexenediols by the haloalkane dehalogenase LinB from Sphingobium indicum B90A
Technical hexachlorocyclohexane (HCH) and lindane are obsolete pesticides whose former production and use led to widespread contaminations posing serious and lasting health and environmental risks. Out of nine possible stereoisomers, α-, β-, γ-, and -HCH are usually present at contaminated sites, and research for a better understanding of their biodegradation has become essential for the development of appropriate remediation technologies. Because haloalkane dehalogenase LinB was recently found responsible for the hydroxylation of β-HCH, δ-HCH, and δ-pentachlorocyclohexene (δ-PCCH), we decided to examine whether β- and γ-PCCH, which can be formed by LinA from α-and γ-HCH, respectively, were also converted by LinB. Incubation of such substrates with Escherichia coli BL21 expressing functional LinB originating from Sphingobium indicum B90A showed that both β-PCCH and γ-PCCH were direct substrates of LinB. Furthermore, we identified the main metabolites as 3,4,5,6-tetrachloro-2-cyclohexene-1-ols and 2,5,6-trichloro-2-cyclohexene-1,4-diols by nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry. In contrast to α-HCH, γ-HCH was not a substrate for LinB. On the basis of our data, we propose a modified γ-HCH degradation pathway in which γ-PCCH is converted to 2,5-cyclohexadiene-1,4-diol via 3,4,5,6-tetrachloro-2-cyclohexene- 1-ol and 2,5,6-trichloro-2-cyclohexene-1,4-diol.
Raina, Vishakha,Rentsch, Daniel,Geiger, Thomas,Sharma, Poonam,Buser, Hans Rudolf,Holliger, Christof,Lal, Rup,Kohler, Hans-Peter E.
p. 6594 - 6603
(2008)
Read Online

Method for preparing 2, 5-dichlorophenol through continuous oxidation of p-dichlorobenzene
The invention discloses a method for preparing 2, 5-dichlorophenol by directly oxidizing p-dichlorobenzene in a micro-channel reactor, and belongs to the field of fine chemical engineering. Accordingto the method, the p-dichlorobenzene is used as a raw material, hydrogen peroxide is used as an oxidant, acetic acid is used as a solvent, and one or more of iron, iron oxide or an iron metal complexis/are used as a catalyst to complete the preparation process of the 2, 5-dichlorophenol in a micro-channel reactor system. According to the method, the temperature and the retention time in the reaction process can be strictly controlled, the accumulation of oxygen is reduced, the reaction temperature is accurately controlled, temperature runaway is prevented, and the safety of a reaction deviceis improved; due to the strong mass transfer effect of the micro-channel reactor, the mass transfer effect among the raw materials in the reaction system is enhanced, and the reaction efficiency is greatly improved.
-
Paragraph 0025; 0027; 0028; 0030; 0031; 0033

(2020/01/25)

Method for hydroxylating aromatic compound
The invention provides a method for directly hydroxylating an aromatic compound. The method comprises the following steps: dissolving the aromatic compound in a solvent, adding hydrogen peroxide and anitroxide free radical compound, and reacting. The nitroxide free radical compound is used as a catalyst, hydrogen peroxide is used as an oxidizing agent, and hydroxylation of the aromatic compound is directly catalyzed and oxidized. Compared with a traditional process, the method has the advantages of high product selectivity, mild reaction conditions, reusability of the catalyst, easiness in separation of oxidation products and raw materials and the like.
-
Paragraph 0108-0109

(2020/06/17)

Vanadium-pyridine catalyst for preparing 2, 5-dichlorophenol through catalytic oxidation and synthesis method and application of vanadium-pyridine catalyst
The invention discloses a vanadium pyridine catalyst for preparing 2, 5-dichlorophenol through catalytic oxidation and a synthesis method and application of the vanadium pyridine catalyst. The catalyst is a Py-V complex as shown in the following structural formula, and is prepared by dissolving pyridine-2, 6-dicarboxylic acid in methanol, adding vanadyl acetylacetonate, refluxing, filtering, washing, drying and the like. The operation steps are simple and easy to control, the yield is 60% or above in terms of vanadium, the whole synthesis process is short in time consumption, and the method issuitable for industrial production. In the process of preparing 2, 5-dichlorophenol through catalytic oxidation of 1, 2, 4-dichlorobenzene, the Py-V complex is adopted as a catalyst, the excessive oxidation of 2, 5-dichlorophenol can be effectively inhibited while the catalytic efficiency is improved, the excessive oxidation product can be controlled to be 10% or below, the selectivity of 2, 5-dichlorophenol reaches 90% or above, and the oxidation reaction efficiency and yield are obviously improved.
-
Paragraph 0025-0027

(2020/11/09)

A new process to prepare 3,6-dichloro-2-hydroxybenzoic acid, the penultimate intermediate in the synthesis of herbicide dicamba
Glyphosate [N-(phosphonomethyl)glycine] is a broad spectrum, post-emergent herbicide that is among the most widely used agrochemicals globally. Over the past 30 years, there has been a development of glyphosate-resistant weeds, which pose a significant challenge to growers and crop scientists, resulting in lower crop yields and increased costs. 3,6-Dichloro-2-methoxybenzoic acid (dicamba) is the active ingredient in XtendiMax a standalone herbicide developed by Bayer Crop Science to control broadleaf weeds, including glyphosate-resistant species. 3,6-Dichloro-2-hydroxybenzoic acid (3,6-DCSA) is the penultimate intermediate in the synthesis of dicamba. Existing dicamba manufacturing routes utilize a high temperature, high pressure Kolbe-Schmitt carboxylation to prepare 3,6-DCSA. Described in this Letter is a new, non-Kolbe-Schmitt process to prepare 3,6-DCSA from salicylic acid in four chemical steps.
Walker, Daniel P.,Harris, G. Davis,Carroll, Jeffery N.,Boehm, Terri L.,McReynolds, Matthew D.,Struble, Justin R.,van Herpt, Jochem,van Zwieten, Don,Koeller, Kevin J.,Bore, Mangesh
p. 1032 - 1036
(2019/03/17)

A dichlorophenol synthesis method (by machine translation)
The present invention provides a kind of dichlorophenol synthetic method, comprises the following steps: S1, will be 1, 4 - dichlorobenzene alkylation reaction, to obtain the 1, 4 - dichloro - 2 - isopropyl benzene; or the 1, 3 - dichlorobenzene alkylation reaction, to obtain the 1, 3 - dichloro - 4 - cumene; or the 1, 2 - dichlorobenzene alkylation reaction, to obtain 1, 2 - dichloro - 4 - cumene; S2, to the 1, 4 - dichloro - 2 - cumene in alkyl, 1, 3 - dichloro - 4 - cumene in alkyl or 1, 2 - dichloro - 4 - alkyl in the cumene, through oxidation, the formula x structure obtained dichloro peroxide; S3, will the catalytic decomposition of the peroxide states two chlorine respectively, to obtain the dichlorophenol and acetone. The present invention provides a method for synthesizing of the dichlorophenol obtained the product content is high, the three waste less generation, mild reaction conditions, easy operation, low production cost. (by machine translation)
-
Paragraph 0032; 0048; 0050; 0057; 0059

(2019/06/05)

Method using iron-carrying activated carbon to catalyze 1,4-dichlorobenzene hydroxylation to prepare 2,5-dichlorophenol
The invention relates to a method using iron-carrying activated carbon to catalyze 1,4-dichlorobenzene hydroxylation to prepare 2,5-dichlorophenol. The method is characterized in that various activated carbon processed by nitric acid and H2O2 is used as the carrier to introduce active components Fe(NO3)3 of different mass through an impregnation method to prepared a Fe-AC catalyst for subsequent reaction; the reaction uses 1,4-dichlorobenzene as the substrate, acetonitrile as the solvent and H2O2 as the oxidizing agent; the reaction is performed in a r round-bottom flask connected with a reflux condensation device, 30% H2O2 solution is slowly fed through a peristaltic pump at constant speed or directly fed into the round-bottom flask in one step, and continuous stirring and heating are performed for a certain period of time during the reaction to obtain the 2,5-dichlorophenol; iron content in the Fe/AC is 0-0.5mmol/g; the mass ratio of p-dichlorobenzene to the Fe/AC is 1:0.1-1:0.5; themole ratio of the p-dichlorobenzene to the H2O2 is 1:1.5-1:29.6; reaction temperature is 30-80 DEG C; reaction time is 10-300 minutes. The method has the advantages that 10mL of 30% H2O2 is added into optimal 0.3g of 0.20mmol/g Fe/HAC-j, 6.63mmol p-dichlorobenzene and 10mL of acetonitrile in one step to perform reaction at 60 DEG C for 2 hours, p-dichlorobenzene conversion rate can reach 70.9%, the yield of the 2,5-dichlorophenol is 39.5%, the selectivity of the 2,5-dichlorophenol is 55.8%, and the whole reaction process is clean and efficient and conforms to the green development concept.
-
Paragraph 0020-0027

(2019/01/23)

Ammonium Salt-Catalyzed Highly Practical Ortho-Selective Monohalogenation and Phenylselenation of Phenols: Scope and Applications
An ortho-selective ammonium chloride salt-catalyzed direct C-H monohalogenation of phenols and 1,1′-bi-2-naphthol (BINOL) with 1,3-dichloro-5,5-dimethylhydantoin (DCDMH) as the chlorinating agent has been developed. The catalyst loading was low (down to 0.01 mol %) and the reaction conditions were very mild. A wide range of substrates including BINOLs were compatible with this catalytic protocol. Chlorinated BINOLs are useful synthons for the synthesis of a wide range of unsymmetrical 3-aryl BINOLs that are not easily accessible. In addition, the same catalytic system can facilitate the ortho-selective selenylation of phenols.
Xiong, Xiaodong,Yeung, Ying-Yeung
p. 4033 - 4043
(2018/05/22)

A 2, 5 - dichlorophenol green synthesis method (by machine translation)
The invention belongs to the field of fine organic chemical industry, to provide a paradichlorobenzene as raw material to direct hydroxylation to prepare 2, 5 - dichlorophenol green synthesis method. In the specific content is 0.5 - 90 °C and under the normal pressure, paradichlorobenzene, hydrogen peroxide and a solvent in the reaction under the mesoporous catalyst 60 - 480 min, one-step reaction can be directly obtained after the separation of 2, 5 - dichlorophenol product, product purity ≥ 99.5%, the product yield can reach 85%. The catalyst is a mesoporous catalyst, mesoporous molecular sieve type is SBA - 15, Ti - MWW, MCM - 41, MCM - 48, MSU - 2, Ti - MWW, MCM - 41, MCM - 48, MSU - 2, solid acid type as phosphorus, sulfur, manganese, tungsten, nickel, cobalt, iron, molybdenum, zinc, [...] solid acid. Hydrogen peroxide and benzene molar ratio of 1:1 - 8:1, the amount of a catalyst is the material of the total amount of 1 - 15%, solvent is methanol, ethanol, propanol, isopropanol, toluene, DMSO, tertiary butyl alcohol, acetone, butanone and acetonitrile or their mixed solvent; hydrogen peroxide concentration is 27.5% -50%; to dichlorobenzene and solvent molar ratio of 1:1 - 1:50. (by machine translation)
-
Paragraph 0012-0019

(2019/01/08)

A 2, 5 - dichlorophenol preparation method
The invention provides a preparation method of 2, 5-dichlorophenol. The preparation method of the 2, 5-dichlorophenol comprises the following steps of pretreatment of catalyst and assistant agents, 1, 4-dichlorobenzene one-step-method product synthesizing, continuous rectification of 2, 5-dichlorophenol and recycling of a substrate and solvent. By the preparation method, the catalyst and the assistant agents are pretreated, the catalytic performance and the catalytic effect of the catalyst can be improved effectively, the efficiency and the yield of synthesis reaction are improved, the use level of the catalyst and the use level of the assistant agents can be reduced obviously, production cost is reduced, heavy components are reduced, and follow-up separation and purification operation is facilitated. Synthetic reaction products are rectified, separated and purified, the purity of the obtained 2, 5-dichlorophenol is greater than 99.5%, the purify of the 1, 4-dichlorobenzene, the solvent and water which are obtained by recycling is greater than 99%, the recycled raw material and the recycled solvent can be directly used for next synthetic reaction, the production cost is reduced, and environmental protection is facilitated.
-
Paragraph 0037; 0038; 0039; 0040; 0041; 0042; 0043-0121

(2017/08/25)

Preparation method of 2,5-dichlorophenol
The invention provides a preparation method of 2,5-dichlorophenol, and belongs to the field of preparation of compounds. The preparation method comprises the following steps: taking 1,4-dichlorobenzene as a raw material and taking a combination of one or more of water, methanol, acetonitrile and acetic acid as a solvent under the effects of an oxidizing agent, a metal porphyrin catalyst and a cocatalyst, and reacting at the temperature of 5-80 DEG C for 0.5-20 hours to obtain 2,5-dichlorophenol. By a catalyst system, efficiency and yield of oxidation reaction can be improved remarkably, reaction conditions are gentle relatively, side effects are less, products are separated favorably, the reaction time is greatly shortened, and the 2,5-dichlorophenol can be industrially produced on a large scale.
-
Paragraph 0024-0061

(2017/09/12)

A method for the synthesis of 2, 5 - dichlorophenol (by machine translation)
The invention relates to a 2, 5?Dichiorophenol synthetic method, which belongs to the technical field of the synthesis of the key intermediate chamber. The invention is composed of a pure chlorization generated 1, 2, 4?Trichlorobenzene and santochlor is easy to separate, thereby avoiding the difficulties caused by the separating of the high production cost and low production efficiency; because the 1, 2, 4?Trichlorobenzene and to two chiorophenoxy can be obtained respectively 2, 5?Dichiorophenol, utilization rate of raw materials is high, thereby avoiding the waste of the by-product, so that the production cost is greatly reduced. In addition, the two paradichlorbenzene through two different method to obtain 2, 5?Dichiorophenol. The synthesis technique of this invention is simple, the production cost is low, the utilization rate of raw materials is high, and the craft there are few by-products, less generation of three wastes, is more suitable for large-scale industrial production. (by machine translation)
-
Paragraph 0067

(2016/10/09)

Method and specialized device for tubular diazotization preparation of 2,5-dichlorophenol
The invention discloses a method and specialized device for tubular diazotization preparation of 2,5-dichlorophenol. The specialized device comprises a mixer, a tubular reactor and a hydrolysis kettle which are sequentially connected through pipelines, the mixer is connected with a first blending kettle for inputting a mixed solution of 2,5-dichloroaniline and H2SO4 and a second blending kettle for inputting a diazotization reagent separately, the first blending kettle is sequentially connected with a first safety valve, a first metering pump and a first flow meter through a first bottom valve and then connected with the mixer, and the second blending kettle is sequentially connected with a second safety valve, a second metering pump and a second flow meter through a second bottom valve and then connected with the mixer; the first metering pump and the first flow meter form a feedback loop, and the second metering pump and the second flow meter form a feedback loop. An inlet of the hydrolysis kettle is communicated with an outlet of the tubular reactor, a water knockout vessel is installed on the hydrolysis kettle, and a first pulsation damper and a second pulsation damper are arranged on a pipeline between the first blending kettle and the tubular reactor and a pipeline between the second blending kettle and the tubular reactor respectively.
-
Paragraph 0037-0044

(2017/07/19)

The Catalyst-Controlled Regiodivergent Chlorination of Phenols
Different catalysts are demonstrated to overcome or augment a substrate's innate regioselectivity. Nagasawa's bis-thiourea catalyst was found to overcome the innate para-selectivity of electrophilic phenol chlorination, yielding ortho-chlorinated phenols that are not readily obtainable via canonical electrophilic chlorinations. Conversely, a phosphine sulfide derived from 2,2′-Bis(diphenylphosphino)-1,1′-binaphthyl (BINAP) was found to enhance the innate para-preference of phenol chlorination.
Maddox, Sean M.,Dinh, Andrew N.,Armenta, Felipe,Um, Joann,Gustafson, Jeffrey L.
supporting information
p. 5476 - 5479
(2016/11/17)

Method for preparing 2,5-dichlorophenol from 2,5-dichloro phenol ether
The invention discloses a method for preparing 2,5-dichlorophenol from 2,5-dichloro phenol ether. 2,5-dichloro phenol ether and an acidic substance are subjected to acidic hydrolysis reaction under the catalytic action of a phase transfer catalyst; the reaction temperature is 110-170 DEG C; the reaction pressure is 0.3-3.0MPa; and the product is subjected to post-treatment to obtain 2,5-dichlorophenol. By the method, the 2,5-dichlorophenol content in the product is greater than 97.5%; the yield of 2,5-dichloro phenol ether by 2,5-dichlorophenol is greater than 95%; the obtained 2,5-dichlorophenol can be directly recycled in synthesis of a dicamba intermediate 3,6-dichlorosalicylic acid as a raw material; and a by-product methine halide can be applied to alkylated synthetic dicamba of the 3,6-dichlorosalicylic acid, so that resource cyclic utilization of wastes is achieved; the target of clean production is achieved; and the method is simple to operate, high in hydrolysis conversion rate, good in environmental benefits and easy to industrialize, and has relatively good application value.
-
Paragraph 0033; 0034

(2016/12/01)

Using 2,5-di- chlorine phenolic ether preparing 2,5-dichlorophenol method
The invention provides a method for preparing 2,5-dichlorophenols by using 2,5-dichlorphenol ether, under phase-transfer catalyst effect and existence of an alkalescence substance, 2,5-dichlorphenol ether is performed with a basic hydrolysis reaction in a solvent, reaction temperature is 120-210 DEG C, reaction pressure is 0.3-3.0MPa, and 2,5-dichlorophenols can be obtained by post-treatment and acidification of products. According to the invention, 2,5-dichlorphenol ether is used for effectively preparing 2,5-dichlorphenol ether, and 2,5-dichlorphenol ether content in the products is greater than 97%, 2,5-dichlorphenol ether yield is greater than 95%, the obtained 2,5-dichlorophenols can be taken as a raw material for directly reusing into synthesis of a dicamba intermediate 3,6-dichlorosalicylic acid, So that resource cycle utilization of the waste can be realized, and cleaning production purpose is reached.
-
Paragraph 0011; 0023-0024

(2017/03/25)

PROCESSES FOR PREPARING 2,5-DICHLOROPHENOL
Processes for producing 2,5-dichlorophenol and 3,6-dichloro-2-methoxybenzoic acid are described. Various processes for isomerizing 2,4-dichlorophenol over a zeolite catalyst to form 2,5-dichlorophenol are provided. Processes for preparing 2,5-dichlorophenol including hydroxylating 1,4-dichlorobenzene are also described. The present invention also relates to processes for producing 3,6-dichloro-2-methoxybenzoic acid.
-
Paragraph 0088-0089

(2016/04/26)

For mass production of a 2,5-dichlorophenol process for the preparation of
The invention provides a preparation process for mass production of 2, 5-dichlorophenol. The method comprises the steps of preparing a catalyst; synthesizing a target product through 1, 4-dichlorobenzene by the one-step method; continuously rectifying the product 2, 5-dichlorophenol; recovering a substrate and a solvent. According to the preparation process, the catalyst can obviously increase the synthesizing reaction efficiency and yield; the production cost can be reduced; the heavy components can be decreased; therefore, the subsequent separating and purifying works can be conveniently carried out; the product of the synthetic reaction is rectified, separated and purified, so that the purity of the product 2, 5-dichlorophenol is more than 99.7%; the purity of the recovered raw material, namely, 1, 4-dichlorobenzene and the purity of the solvent and water are more than 99%; the recovered raw material and the solvent can be directly used in the next synthetic reaction; therefore, the production cost can be reduced, and the environment can be protected.
-
Paragraph 0045; 0046; 0047; 0048; 0049; 0050; 0051; 0052

(2017/01/02)

Synthesis of 2, 5 - dichlorophenol (by machine translation)
The invention relates to a synthesis of 2, 5 - dichlorophenol, more in particular to a method for 1, 2, 4 - trichlorobenzene hydrolysis of direct synthesis of 2, 5 - dichlorophenol. The present invention relates to 1, 2, 4 - trichlorobenzene as the raw material, an inorganic or organic base for the hydrolytic agent, sulfonate as a catalyst, the preparation of 2, 5 - dichlorophenol. The process is characterized in that the main advantages: simple process flow, the reaction system is alkaline, low requirements on equipment, 2, 5 - dichlorophenol selective, high yield. (by machine translation)
-
Paragraph 0041; 0042

(2017/04/19)

PROCESSES FOR THE DIAZOTIZATION OF 2,5-DICHLOROANILINES
The present disclosure relates, in general, to processes for converting 2,5- dichloroaniline compounds to the corresponding 2,5-dichlorobenzenediazonium compounds, and further relates to processes for the preparation of 2,5-dichloro- phenol which is a key intermediate used in the manufacture of dicamba.
-
Paragraph 157-160

(2015/07/07)

PROCESS FOR MAKING 2,5-DIHALOGENATED PHENOL
The present invention relates to a process for reacting chemical compounds comprising the step of reacting a compound of formula (IV) wherein Hal is independently selected from CI or Br, and X" is a monovalent anion, in the presence of an inorganic acid, wherein the aqueous inorganic acid has a concentration of at least about 60%, at a temperature of about 140 °C to about 250 °C, to obtain a compound of formula (V) wherein Hal is as defined above.
-
Page/Page column 17

(2015/12/08)

SELECTIVE HYDROLYSIS AND ALCOHOLYSIS OF CHLORINATED BENZENES
The present invention relates to a process for providing a compound of formula (I):, wherein R is hydrogen or R', wherein R' is –(C1-C4)alkyl, and Hal is a halogen, the process comprising the step of: reacting a compound of formula (II) wherein Hal is defined as above, with an alkali metal alkoxide of the formula XOR', wherein X is an alkali metal, and R' is defined as above.
-
Page/Page column 15

(2015/04/22)

PROCESS FOR HYDROLYZING 1,2,4-TRIHALOBENZENE
The present invention relates to a process for providing a compound of formula (I): wherein Hal is a halogen, the process comprising the step of: reacting a compound of formula (II) wherein Hal is defined as above, with an alkali metal sulfite of the formula X2SO3 and an alkali metal hydroxide of the formula YOH, wherein X and Y are independently selected from an alkali metal.
-
Page/Page column 11

(2015/04/22)

Formation of chlorinated phenols, dibenzo-p-dioxins, dibenzofurans, benzenes, benzoquinnones and perchloroethylenes from phenols in oxidative and copper (II) chloride-catalyzed thermal process
Formation of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and chlorinated phenols on CuCl2 from unsubstituted phenol and three monochlorophenols was studied in a flow reactor over a temperature range of 100-425 °C. Heated nitrogen gas streams containing 8.0% oxygen were used as carrier gas. The 0.00024 mol of unsubstituted phenol and 0.00039 mol of each monochlorophenol were passed through a 1 g and 1 cm SiO2 particle containing 0.5% (Cu by mass) CuCl2. Chlorination preferentially occurred on ortho-(2, 6) and para-(4) positions. Chlorination increased up to 200 °C, and thereafter decreased as temperature increased. Chlorination of phenols plays an important role in the formation of the more chlorinated PCDD/Fs. Chlorinated benzenes are formed possibly from both chlorination of benzene and chlorodehydroxylation of phenols. Chlorinated phenols with ortho chlorine formed PCDD products, and major PCDD products were produced via loss of one chlorine. For PCDF formation, at least one unchlorinated ortho carbon was required.
Ryu, Jae-Yong
p. 1100 - 1109
(2008/12/21)

Catalysis and inhibition of ester hydrolysis in the presence of resorcinarene hosts functionalized with dimethylamino groups
Complexation and catalysis of two calixresorcinarene (RES) derivatives with nucleophilic N,N-dimethylamino functions attached to their upper rims in the hydrolysis of carboxylate and sulfonate esters of 4-nitrophenol and 2,4-dinitrophenol have been investigated. Rate constants obey the complexation equation: kobs = kb × Ks + k c[Host]/Ks + [Host] Values of the dissociation constant (Ks) of the complexes are within the range exhibited by other systems such as cyclodextrins-ester complexes. The reactions of sulfonate esters only exhibit inhibition by the macrocyclic hosts. The reactions of the carboxylate esters exhibit catalysis and inhibition depending on the pH of the system. It is proposed that the dimethylamino function in RES3 and RES5 behaves as a nucleophile to form a reactive acylammonium species which subsequently decomposes and regenerates the catalytic amine. In the reaction of substituted phenyl acetates with RES3 the effective charge on the leaving oxygen in the complexed state (+0.88) is slightly more positive than that in the free ester (+0.70). The effective charge on the leaving oxygen in the transition structure is substantially more positive (+0.04 units) than in a model intramolecular reaction of tertiary dimethylamines with aryl esters (-0.53 units). The influence of the host on the reaction in the complex includes an electronic component which is ascribed to solvation of the transition structure of the rate-limiting step by water molecules located within the cavity of the host. It is suggested that this solvation is stronger than that occurring in the transition state for the model intramolecular reaction. Copyright
Cevasco, Giorgio,Thea, Sergio,Vigo, Daniele,Williams, Andrew,Zaman, Flora
p. 630 - 636
(2008/02/08)

A comparative study of the hydrolysis pathways of substituted aryl phosphoramidate versus aryl thiophosphoramidate derivatives of stavudine
A comparative study of aryl phosphoramidate and aryl thiophosphoramidate derivatives of 2′,3′-didehydro-2′,3′-dideoxythymidine (d4T) was performed. The study focused on the nature of the substituents and the influence of a thiophosphoramidate in the structure of these derivatives. The rate of alkaline hydrolysis of these two types of d4T derivatives indicated that replacement of oxygen with sulfur decreases the rate of hydrolysis by twofold. Additionally, the activation energy (Ea) for the sulfur analogs is comparatively higher than that of the oxygen analogs. Notably, an intermediate was formed in the hydrolysis reaction of the sulfur analogs of d4T that was absent in the case of the oxygen analog, and the tentative structure of the intermediate was proposed based on LC/mass spectroscopy data. Using both HPLC and 31P-NMR techniques, we identified the hydrolysis product of the phosphoramidate derivatives and were able to show in in vitro studies that porcine liver esterase can hydrolyze the methyl ester portion of the phosphoramidate derivatives. Aryl phosphoramidate derivatives of d4T were 1000-fold more active than the corresponding aryl thiophosphoramidate derivatives, indicating that the energy of activation of hydrolysis of these phosphoramidate derivatives plays a significant role in their biological potency.
Venkatachalam,Yu,Samuel,Qazi,Pendergrass,Uckun
p. 665 - 683
(2007/10/03)

Oxidation process
Preparation of 2,5-dichlorophenol by selectively oxidizing 1,4-dichlorobenzene using a peroxo-, hydroperoxo-, superoxo- or alkylperoxo-vanadium species in the presence of an α-hydroxy-, dibasic-, tribasic- or sulfonic acid.
-
(2008/06/13)

Electroreduction of Organic Compounds, 34 [1]. Cathodic Dehalogenation of Chloroarenes with Electron-Donating Substituents
The electrochemical reduction of chlorinated arenes with electron-donating substituents, i.e. chlorotoluenes, -anisoles and -phenols, is studied. Preparative electrolyses are run in various solvent-supporting electrolytes under potentiostatic and galvanostatic conditions at lead or carbon cathodes. A partial and mostly regioselective hydrodechlorination of compounds with two or more chloro substituents is possible under suitable conditions. The replacement of one single chloro substituent, in particular in a para-position, is difficult. Highly toxic and persistent oligochloro derivatives are thus transformed into less problematic compounds with a low degree of chlorination. The chlorine content of real-life materials such as extracts of soil contaminated with chlorinated phenols and Nitrofen can also be significantly decreased by electroreduction.
Kranz, Olaf,Voss, Jürgen
p. 1187 - 1200
(2007/10/03)

PROCESS FOR THE HYDROXYLATION OF 1,4-DICHLOROBENZENE
Preparation of 2,5-dichlorophenol by selectively oxidizing 1,4-dichlorobenzene using a peroxo-, hydroperoxo-, superoxo- or alkylperoxo-metal species in the presence of formic or an alkanoic acid.
-
(2008/06/13)

Kinetics of chlorination of phenol and monosubstituted phenols by t-butyl hypochlorite in aqueous alkaline medium
The kinetics of chlorination of the parent and sixteen monosubstituted phenols (2-chloro, 2-methyl, 2-carboxy, 2-nitro, 3-chloro, 3-methyl, 3-carboxy, 4-fluoro, 4-chloro, 4-bromo, 4-methyl, 4-ethyl, 4-methoxy, 4-carboxy, 4-acetyl and 4-nitro) by t-BuOCl have been studied in aqueous alkaline medium. The rates of reactions show first order kinetics each in |t-BuOCl| and |XC 6H4OH| and inverse first order in |OH-|. Variation in either ionic strength or addition of reaction product has no significant effect on the rates of reactions, while lowering of the dielectric constant of the medium increases the rate. The rates are measured at different temperatures and the activation parameters for all the phenols computed. A mechanism involving the electrophilic attack of phenoxide ions by HOCl in the rate determining step is suggested. The rates decrease in the order: 3-CH 3 > 2-CH3 > 4-OCH3 > 4-CH3 > 4-C2H5 > H > 3-Cl > 3-COO- > 4-F > 2-COO- > 4-Br > 2-Cl > 4-Cl > 4-COO- > 4-COCH3 > 2-NO2 > 4-NO2. Hammett equation of the type, log k = -3.44 - 2.35 ρ is found to be valid for substituent effects. The enthalpy and entropy of activation are correlated.
Moodithaya,Gowda, B. Thimme
p. 420 - 425
(2007/10/03)

Dechlorination of lindane, dieldrin, tetrachloroethane, trichloroethene, and PVC in subcritical water
Pure water has been used to dechlorinate aliphatic organics without the need for catalysts or other additives. Dehydrohalogenation (loss of HCl with the formation of a double bond) occurred at temperatures as low as 105-200 °C for 1,1,2,2-tetrachloroethane, lindane (1,2,3,4,5,6-hexachlorocyclohexane, γ-isomer), and dieldrin (1,2,3,4,10,10-hexachloro-6,7-epoxy-1,4,4a,5,6,7,8,8a-octahydro-endo, exo-1,4:5,8-dimethanonaphthalene). Complete loss of the parent compounds was achieved in less than 1 h at 150, 200, and 300 °C for 1,1,2,2-tetrachloroethane, lindane, and dieldrin, respectively. The initial dechlorination of lindane had an activation energy of 84 kJ mol-1 with an Arrhenius pre-exponential factor of 1.5 x 106 s-1. Dehydrohalogenation of lindane formed trichlorobenzenes, followed by subsequent hydrolysis and hydride/chloride exchange to form chlorophenols, lower chlorobenzenes, and phenol as the major final product. Reaction of poly(vinyl chloride) at 300 °C for 1 h formed aromatic hydrocarbons ranging from benzene to anthracene and a char residue with a ca. 1:1 carbon-to-hydrogen ratio (mol/mol). The residue contained 1 wt % of chlorine compared to 57 wt % chlorine in the original polymer. All compounds tested yielded chloride ion as the major product (at higher temperatures), indicating that complete dechlorination of some aliphatic organochlorines may be feasible.
Kubatova, Alena,Lagadec, Arnaud J. M.,Hawthorne, Steven B.
p. 1337 - 1343
(2007/10/03)

Oxidation process
Preparation of 2,5-dichlorophenol by selectively oxidizing 1,4-dichlorobenzene using a peroxo-, hydroperoxo-, superoxo- or alkylperoxo-metal species in the presence of an α-hydroxy-, dibasic-, tribasic- or sulfonic acid.
-
(2008/06/13)

Kinetics and mechanism of chlorination of phenol and substituted phenols by sodium hypochlorite in aqueous alkaline medium
The kinetics of chlorination of the parent and thirteen substituted phenols (2-methyl, 2-chloro, 2-carboxy, 3-methyl, 3-chloro, 3-carboxy, 4-methyl, 4-ethyl, 4-chloro, 4-bromo, 4-carboxy, 4-acetyl and 4-nitro phenols) by NaOCl have been studied in aqueous alkaline medium under varying conditions. The rates show first order kinetics each in [NaOCl] and [(X)C6H4(OH)] and inverse first order in [OH-]. Variation in ionic strength of the medium and addition of Cl have no significant effect on the rates of reactions. The rates of the reactions are measured at different temperatures and the activation parameters for all the phenols computed. A mechanism involving the electrophilic attack of the phenoxide ions by NaOCl in the rate determining step has been considered. The values of the pre-equilibrium and the rate determining steps have been calculated for all the phenols. The rates decrease in the order: 3-CH3 >2-CH3 >4-C2H5 = 4-CH3 >phenol >3-COO = 3-Cl > 2-COO >4-COO >2-Cl ? 4-Cl ? 4-Br > 4-COCH3 >4-NO2. Hammett plot of the type, log kobs = -2.88 -3.2980σ is found to be valid. The correlation between the enthalpies and the free energies of activations is reasonably linear with an isokinetic temperature of 300 K. Further, the energies of activation of all the phenols are optimised corresponding to the log A of the parent phenol through the equation, Ea = 2.303 RT (log A - log kobs). Similarly log A values of all the phenols are optimised corresponding to the Ea of PhOH through the equation, log A = log kobs + Ea/2.303RT. Ea increases with the introduction of electron-withdrawing groups into the benzene ring, while the introduction of the electron-releasing groups lowers Ea for the reaction. Similarly log A decreases with the substitution of electron-withdrawing groups, while log A increases on substitution with the electron-releasing groups.
Gowda,Mary
p. 1196 - 1202
(2007/10/03)

Oxidation process
Preparation of 2,5-dichlorophenol by selectively oxidizing 1,4-dichlorobenzene using a peroxo-, hydroperoxo-, superoxo- or alkylperoxo-metal species in the presence of form or an alkanoic acid.
-
(2008/06/13)

Photochemical behaviour of 1,4-dichlorobenzene in aqueous solution
Several photoproducts were identified in the direct photolysis of 1,4-dichlorobenzene (1,4-DCB) in air-saturated aqueous solution, namely 4-chlorophenol, hydroquinone, hydroxybenzoquinone, and 2,5-dichlorophenol. In the absence of oxygen the latter is not formed and phenol was detected, but the unexpected formations of 4,4′-dichlorobiphenyl, 2,4′,5-trichlorobiphenyl, and a terphenyl derivative are observed. Mechanisms are proposed to explain the formations of identified photoproducts. The phototransformation of 1,4-DCB may be photoinduced by NO3- or FeIII salts. The main primary product is 2,5-dichlorophenol, which results from a hydroxylation without dechlorination. Some other products have been identified in particular 4-chlorophenol and 2,5-dichlorobenzoquinone in the case of FeIII salts.
Meunier,Pilichowski,Boule
p. 1179 - 1186
(2007/10/03)

Reactions within Association Complexes: The Reaction of Imidazole with Substituted Phenyl Acetates in the Presence of Detergents in Aqueous Solution
The bimolecular rate constants for reaction of imidazole with phenyl acetates complexed with sodium dodecyl sulfate (SDS) or cetyltrimethylammonium bromide (CTAB) micelles obey Bronsted equations with βlg similar to that of the reaction in aqueous solution. The dissociation constants of ester (KS) and the hypothetical dissociation constant (KTS) of the transition state of the micelle complexes obey Hansch equations with similar sensitivities (p) to π (-0.66 and -0.589 for KS and -0.735 and -0.495 for KTS, respectively). The slopes also indicate that the microsolvation environments associated with the transition state and the complexed ester have aqueous character. The relative values of KTS and KS indicate that the transition state of the reaction of imidazole with ester is more weakly complexed to both micelles than is the reactant ester. Log KTS values are linear functions of log KS for reactions with both CTAB and SDS; the slopes are, respectively, -0.893 and -1.19 consistent with a slightly more "water-like" medium for the transition state than for the site of binding of ester with CTAB-micelle and slightly less for the SDS-micelle. The results for ester and transition state are consistent with the location of the phenyl residue in a hydrophobic region that possesses water molecules. It is concluded that the acetyl group in the complexed transition state is located in an aqueous part of the Stern region, whereas the phenyl residue is in a part of the Stern region that possesses alkane components. The derived kinetic and complexation parameters in these experiments refer to micelles with Stern regions that have been maintained at constant ionic compositions.
Pirinccioglu, Necmettin,Zaman, Flora,Williams, Andrew
p. 2537 - 2543
(2007/10/03)

Natural formation of chlorinated phenols, dibenzo-p-dioxins, and dibenzofurans in soil of a Douglas fir forest
The natural formation of 4-MCP, 24/25- and 26-DCP, and 245-TrCP was detected in four selected areas of a rural Douglas fir forest where the humic layer was spiked in situ with a solution of Na37Cl and covered by an enclosure, after 1 year of incubation. Chlorinated phenols (CP) can be formed naturally from organic matter and inorganic chloride by either de novo synthesis or chloroperoxidase (CPO)-catalyzed chlorination. The natural CP congeners were found to be present in high concentrations in soil compared to the other congeners, except for 245-TrCP which was present in a relatively low concentration. This study did not reveal which source, natural or anthropogenic, caused the observed concentrations. Some 20 chlorinated dibenzo-p-dioxins and dibenzofurans (CDD/F) were found to be formed naturally in soil of the Douglas fir forest; the formation of three 2,3,7,8-substituted congeners, 2378-TeCDD, 12378-PeCDD, and 123789-HxCDD, deserves special attention. A formation mechanism has been proposed which starts from naturally formed CP congeners and which probably involves peroxidase mediation. Chlorination of CDD/F congeners by the CPO-mediated reaction cannot be ruled out, but seems to be less likely due to the absence of several predicted congeners. The natural formation of 4-MCP, 24/25- and 26-DCP, and 245-TrCP was detected in four selected areas of a rural Douglas fir forest where the humic layer was spiked in situ with a solution of Na37Cl and covered by an enclosure, after 1 year of incubation. Chlorinated phenols (CP) can be formed naturally from organic matter and inorganic chloride by either de novo synthesis or chloroperoxidase (CPO)-catalyzed chlorination. The natural CP congeners were found to be present in high concentrations in soil compared to the other congeners, except for 245-TrCP which was present in a relatively low concentration. This study did not reveal which source, natural or anthropogenic, caused the observed concentrations. Some 20 chlorinated dibenzo-p-dioxins and dibenzofurans (CDD/F) were found to be formed naturally in soil of the Douglas fir forest; the formation of three 2,3,7,8-substituted congeners, 2378-TeCDD, 12378-PeCDD, and 123789-HxCDD, deserves special attention. A formation mechanism has been proposed which starts from naturally formed CP congeners and which probably involves peroxidase mediation. Chlorination of CDD/F congeners by the CPO-mediated reaction cannot be ruled out, but seems to be less likely due to the absence of several predicted congeners.
Hoekstra, Eddo J.,De Weerd, Henk,De Leer, Ed W. B.,Brinkman, Udo A.Th.
p. 2543 - 2549
(2007/10/03)

Oxidation process
Process for oxidizing 1,4-dichlorobenzene using a secondary synthesized zeolites or zeolite-like metallosilicates or a primary synthesized zeolite-like metallosilicate and a peroxide.
-
(2008/06/13)

Effective charge development in the transfer of the acetyl group between nucleophiles in acetonitrile solution: Acetolysis and butylaminolysis of substituted phenyl esters
Equilibrium and rate constants have been measured for the phenolyses of acetic anhydride in acetonitrile solution. Acetolysis of substituted phenyl acetates by acetate ion possesses a Bronsted βlg value of -1.50 which, together with a βeq value of 2.86, indicates substantial fission of the C-OAr bond in the transition structure. The value of βeq is employed to identify the rate-limiting steps in aminolyses in acetonitrile. Butylaminolysis of substituted phenyl acetates in acetonitrile solution yields amide and substituted phenolate anion and the kinetics obey the general rate law: Rate = k1[ester][amine] + k2[ester][amine]2 + k3[ester][amine][18-crown-6] Free energy plots of log k1 and log k2 exhibit breaks near pKaArOH values of 9 and 8, respectively, and these can be interpreted by a mechanism which involves a common zwitterionic adduct T±, which partitions to give the product by two routes: A involving direct expulsion of the phenolate ion leaving group (k1 parameter) and B involving proton transfer prior to phenolate ion expulsion (k2 parameter). The formation of T± is rate-limiting for the A path and C-OAr bond fission is rate-limiting for the B mechanism.
Maude, Antony B.,Williams, Andrew
p. 179 - 183
(2007/10/03)

Selective and one-pot formation of phenols by anodic oxidation
Direct monohydroxylation of benzene and substituted benzenes was successfully performed by anodic oxidation to form the corresponding phenol derivatives in good yields. The anodic oxidation was generally carried out in a mixed solvent of trifluoroacetic acid and dichloromethane containing triethylamine using a divided cell equipped with a platinum plate as the anode, a carbon rod as the cathode. Benzene derivatives having electron withdrawing groups were suitable for the present electrochemical oxidation. It was clarified that aryltrifluoroacetates were formed as the initial products from the reaction of the radical cations, generated by one electron transfer from the substrates, with trifluoroacetic acid, followed by hydrolysis during work-up to give the corresponding phenols.
Fujimoto, Kazuo,Tokuda, Yuichiro,Maekawa, Hirofumi,Matsubara, Yoshiharu,Mizuno, Takumi,Nishiguchi, Ikuzo
p. 3889 - 3896
(2007/10/03)

Para-hydroxyalkylation of hydroxylated aromatic compounds
Hydroxylated aromatic compounds devoid of substituents in the para-position to the hydroxyl group thereof are para-hydroxyalkylated, e.g., into optionally substituted p-hydroxymandelic acid compounds, more particularly p-hydroxymandelic acid and 3-methoxy-p-hydroxymandelic acid, by condensing same with an organic carbonyl compound in the presence of a quaternary ammonium hydroxide.
-
(2008/06/13)

Complexation catalysis: effective charge development in the aminolysis of phenyl esters in chlorobenzene catalysed by crown ethers
Kinetics of the butylaminolysis of substituted phenyl acetates in chlorobenzene in the presence of a variety of crown ethers obey the following rate law.Rate = kb2 + kc The individual rate constants fit Broensted-type relationships: log kb = -0.75 pKa + 4.21, log kc = -0.58 pKa + 3.41, log kc = -0.61 pKa + 3.18, where pKa refers to the ionization of the phenol in aqueous solution.The Broensted β1g values for kb and kc are calibrated with the value of βeq recently determined for acetyl transfer between phenolate ions in chlorobenzene.The sensitivity, β1g, of kc is consistent with the rate-limiting formation of a crown ether-zwitterion adduct with subsequent fast (non-rate-limiting) ArO-C bond fission.The Broensted data for kb when calibrated by βeq is consistent with rate-limiting proton transfer from zwitterion to base. 18-Crown-6 enables proton transfer to occur between phenol and butylamine in chlorobenzene according to the equation: BuNH2 + ArOH + Crown Bu-NH3+*Crown + ArO-. The equilibrium constant (K) for the above reaction with a series of substituted phenols has a Broensted selectivity (β) of 2.1 compared with that for the ionization of phenols in water.
Maude, Antony B.,Williams, Andrew
p. 691 - 696
(2007/10/02)

Charge Description of Base-Catalyzed Alcoholysis of Aryl Phosphodiesters: A Ribonuclease Model
The release of substituted phenol from aryl uridine-3'-phosphates is catalyzed by bases and involves cyclization to form the 2',3'-cyclic nucleotide.The rate constants for imidazole and hydroxide ion catalysis (kim and kOH, respectively) obey the Broensted equations (25 deg C and 0.25 M ionic strength) log kim = -0.59 pKArOH + 1.40 (n = 7, r = 0.955) and log kOH = -0.54 pKArOH + 6.68 (n = 9, r = 0.967).General-base-catalyzed release of 4-nitrophenol from the 4-nitrophenyl ester (kB) obeys the Broensted relationship log kB = 0.67 pKBH - 7.50 (n = 7, r = 0.989).Charge changes on base and leaving group atoms as determined from the corresponding β and βeq values do not balance.Comparison with data in the literature indicates that the difference in charge may be assigned to the attacking oxygen (2'-hydroxyl) rather than to the phosphoryl oxygens in the O...PO2... group of atoms.Both P-O bond forming and bond fission components of the reaction are considered to be only weakly advanced in a transition state that lies on a concerted pathway.
Davis, Andrew M.,Hall, Adrian D.,Williams, Andrew
p. 5105 - 5108
(2007/10/02)

The Reactions of Superoxide Ion with Arylhydrazines
Arylhydrazines react with potassium superoxide to give a variety of products, most of which are derived from interaction of aryl radicals with the solvent.Phenylhydrazine in toluene gives three isomeric metylbiphenyls, diphenylmethane and bibenzyl.In pyridine, the products identified were 2-, 3-, and 4-phenylpyridine.A more complex range of products was obtained from substituted phenylhydrazines.Products are consistent with a process in which superoxide ion abstracts hydrogen atoms from the hydrazines giving radical intermediates, including aryl radicals, which react with the solvents.
Crank, George,Gately, Garry E.,Makin, Mohammad I. H.
p. 2499 - 2507
(2007/10/02)

STUDIES ON 1-ARYLOXYSILATRANES, II. - HYDROLYTIC STABILITY OF 1-ARYLOXYSILATRANES
The effect of substituents in the benzene ring on the rate constants of the hydrolysis of 1-aryloxysilatranes was investigated.A good correlation of log k vs. Σ? was obtained suggesting SN2-Si mechanism of the hydrolysis of all the compounds studied.The influence of the salt effect and reaction medium on the rate constant was also examined.The activation energies were determined for six compounds.
Lukasiak, J.,Jamrogiewicz, Z.
p. 167 - 172
(2007/10/02)

THE REACTIONS OF UNACTIVATED ARYL HALIDES WITH SODIUM METHOXIDE IN HMPA; SYNTHESIS OF PHENOLS, ANISOLES, AND METHOXYPHENOLS
Sodium methoxide reacts with dichlorobenzenes in HMPA to give the chloroanisoles as a result of a SNAr process.Excess MeONa then effects the demethylation of the ethers to give the chlorophenols via an SN2 reaction.With tri- and tetrachlorobenzenes the initially formed chloroanisoles can be dealkylated to chlorophenols or can suffer further substitution to give the chlorodimethoxybenzenes; these react with excess MeONa to give the chloromethoxyphenols.The results obtained with the various isomers of the di-, tri-, and tetrachlorobenzenes are presented and discussed on the basis of the electronic effects of the substituents.
Testaferri, L.,Tiecco, M.,Tingoli, M.,Chianelli, D.,Montanucci, M.
p. 193 - 198
(2007/10/02)

Trichlorophenoxy alkanoic acid free of chlorinated dibenzo-p-dioxins
This invention provides as new compositions of matter 2,4,5-trichlorophenoxy acetic acid (2,4,5-T) and (2-2,4,5-trichlorophenoxy) propionic acid (Silvex) including the hydrolyzable salts, aliphatic esters and amides of these acids, which compositions are free of chlorinated dibenzo-p-dioxins.
-
(2008/06/13)

Process for the production of 2,5-dichloro-4-bromophenol
This invention discloses a process for the preparation of 2,5-dichloro-4-bromophenol which comprises reacting a mixture of 2,5-dichlorophenol and 2,4-dichlorophenol with about 0.9 to about 1.2 molar amounts of bromine per mole of 2,5-dichlorophenol and thereafter recovering the 2,5-dichloro-4-bromophenol.
-
(2008/06/13)

Process for producing polyhalogenated phenols
A process for producing polyhalogenated phenol by mixing a polyhalogenated aniline with an aqueous sulfuric acid solution to obtain a suspension of fine particles of polyhalogenated aniline sulfate having the particle size of 50 μ or less, diazotizing the polyhalogenated aniline sulfate to obtain polyhalogenate benzenediazonium sulfate, hydrolyzing the resulting benzenediazonium sulfate by heating it as such, recycling to the diazotization step the aqueous sulfuric acid solution from which the desired polyhalogenated phenol has been separated.
-
(2008/06/13)